U.S. patent number 11,370,298 [Application Number 16/695,620] was granted by the patent office on 2022-06-28 for work vehicle.
This patent grant is currently assigned to Iseki & Co., LTD.. The grantee listed for this patent is Iseki & Co., LTD. Invention is credited to Hidekazu Tsuji.
United States Patent |
11,370,298 |
Tsuji |
June 28, 2022 |
Work vehicle
Abstract
A work vehicle includes front and rear wheels, a transmission
case and a power transmission device. The power transmission device
is housed in the transmission case and is configured to transmit
driving power from an engine to driving wheels. The power
transmission device has a front wheel driving shaft and a
four-wheel drive clutch. The front wheel driving shaft is arranged
in a lower inside portion of the transmission case and is
configured to transmit the driving power to the front wheels. The
four-wheel drive clutch is arranged above the front wheel driving
shaft, and is configured to switch between a two-wheel drive state
in which the driving power is transmitted to the rear wheels, and a
four-wheel drive state in which the driving power is transmitted to
both the front wheels and the rear wheels via the front wheel
driving shaft.
Inventors: |
Tsuji; Hidekazu (Ehime-ken,
JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
Iseki & Co., LTD |
Ehime-ken |
N/A |
JP |
|
|
Assignee: |
Iseki & Co., LTD.
(Matusyama, JP)
|
Family
ID: |
1000006398904 |
Appl.
No.: |
16/695,620 |
Filed: |
November 26, 2019 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20200164741 A1 |
May 28, 2020 |
|
Foreign Application Priority Data
|
|
|
|
|
Nov 28, 2018 [JP] |
|
|
JP2018-222695 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B60K
17/34 (20130101); B60K 17/02 (20130101); B60K
17/22 (20130101); G01M 13/021 (20130101); B60Y
2200/221 (20130101); F16D 25/12 (20130101); F16D
13/52 (20130101) |
Current International
Class: |
B60K
17/34 (20060101); B60K 17/02 (20060101); B60K
17/22 (20060101); G01M 13/021 (20190101); F16D
13/52 (20060101); F16D 25/12 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Winner; Tony H
Assistant Examiner: Stabley; Michael R
Attorney, Agent or Firm: Finnegan, Henderson, Farabow,
Garrett & Dunner, LLP
Claims
What is claimed is:
1. A work vehicle, comprising: a pair of left and right front
wheels and a pair of left and right rear wheels each provided on a
machine body frame; a transmission case arranged below the machine
body frame; and a power transmission device housed in the
transmission case and configured to transmit a driving power from
an engine to driving wheels, the power transmission device
comprising: a front wheel driving shaft arranged in a lower inside
portion of the transmission case and configured to transmit the
driving power to the front wheels; and a four-wheel drive clutch
arranged above the front wheel driving shaft, the four-wheel drive
clutch being configured to switch between a two-wheel drive state
in which the driving power is transmitted to the rear wheels, and a
four-wheel drive state in which the driving power is transmitted to
the front wheels and the rear wheels via the front wheel driving
shaft, wherein the power transmission device further comprises: a
rear wheel driving shaft for driving the rear wheels; and a
four-wheel drive input shaft configured to receive the driving
power from the rear wheel driving shaft and then to transmit the
driving power to the four-wheel drive clutch, wherein the
four-wheel drive input shaft is provided coaxially with the front
wheel driving shaft, and an end portion of the four-wheel drive
input shaft on a downstream side in terms of power transmission is
loosely fitted with an end portion of the front wheel driving shaft
on an upstream side in terms of power transmission.
2. The work vehicle according to claim 1, wherein the four-wheel
drive clutch is arranged to be offset from the front wheel driving
shaft in a horizontal direction and vertical direction.
3. The work vehicle according to claim 1, wherein in the two-wheel
drive state only the rear wheels act as the driving wheels, and in
the four-wheel drive state both the front wheels and the rear
wheels act as the driving wheels.
4. The work vehicle according to claim 1, wherein a
circular-cylindrical convex portion is provided on an end surface
of the end portion of the four-wheel drive input shaft, and a
circular concave portion is formed on an end surface of the end
portion of the front wheel driving shaft.
5. The work vehicle according to claim 4, wherein the convex
portion is loosely fitted into the concave portion so that a gap is
formed between the convex portion and an inner wall of the concave
portion.
6. The work vehicle according to claim 1, wherein the four-wheel
drive clutch is arranged adjacent to an inner wall of the
transmission case.
7. The work vehicle according to claim 6, further comprising: a
sensor configured to detect rotation of a gear for driving the
four-wheel drive clutch, wherein the sensor is provided in the
inner wall of the transmission case.
8. The work vehicle according to claim 1, further comprising: an
implement disposed below the transmission case.
9. A work vehicle, comprising: a set of front wheels and a set rear
wheels provided on a machine body frame; a transmission case
arranged below the machine body frame; and a power transmission
device housed in the transmission case and configured to transmit a
driving power from an engine to driving wheels, the power
transmission device comprising: a front wheel driving shaft
arranged below the transmission case and configured to transmit the
driving power to the front wheels; and a four-wheel drive clutch
arranged offset from the front wheel driving shaft, wherein the
four-wheel drive clutch is configured to switch between a first
drive state in which the driving power is transmitted to the rear
wheels so that the rear wheels act as the driving wheels, and a
second drive state in which the driving power is transmitted to the
front wheels and the rear wheels via the front wheel driving shaft
so that both the front wheels and the rear wheels act as the
driving wheels, wherein the power transmission device further
comprises: a rear wheel driving shaft for driving the rear wheels;
and a four-wheel drive input shaft configured to receive the
driving power from the rear wheel driving shaft and then to
transmit the driving power to the four-wheel drive clutch, wherein
the four-wheel drive input shaft is provided coaxially with the
front wheel driving shaft, and an end portion of the four-wheel
drive input shaft on a downstream side in terms of power
transmission is loosely fitted with an end portion of the front
wheel driving shaft on an upstream side in terms of power
transmission.
10. The work vehicle according to claim 9, wherein the four-wheel
drive clutch is arranged to be offset from the front wheel driving
shaft in a horizontal direction and vertical direction.
11. The work vehicle according to claim 9, wherein a
circular-cylindrical convex portion is provided on an end surface
of the end portion of the four-wheel drive input shaft, and a
circular concave portion is formed on an end surface of the end
portion of the front wheel driving shaft.
12. The work vehicle according to claim 11, wherein the convex
portion is loosely fitted into the concave portion so that a gap is
formed between the convex portion and an inner wall of the concave
portion.
13. The work vehicle according to claim 9, wherein the four-wheel
drive clutch is arranged adjacent to an inner wall of the
transmission case.
14. The work vehicle according to claim 13, further comprising: a
sensor configured to detect rotation of a gear for driving the
four-wheel drive clutch, wherein the sensor is provided in the
inner wall of the transmission case.
15. The work vehicle according to claim 9, further comprising: an
implement disposed below the transmission case.
16. A work vehicle, comprising: a pair of left and right front
wheels and a pair of left and right rear wheels each provided on a
machine body frame; a transmission case arranged below the machine
body frame; and a power transmission device housed in the
transmission case and configured to transmit a driving power from
an engine to driving wheels, the power transmission device
comprising: a front wheel driving shaft arranged in a lower inside
portion of the transmission case and configured to transmit the
driving power to the front wheels; and a four-wheel drive clutch
arranged above the front wheel driving shaft, the four-wheel drive
clutch being configured to switch between a two-wheel drive state
in which the driving power is transmitted to the rear wheels, and a
four-wheel drive state in which the driving power is transmitted to
the front wheels and the rear wheels via the front wheel driving
shaft, wherein the four-wheel drive clutch is arranged adjacent to
an inner wall of the transmission case, and wherein the work
vehicle further comprises: a sensor configured to detect rotation
of a gear for driving the four-wheel drive clutch, wherein the
sensor is provided in the inner wall of the transmission case.
17. A work vehicle, comprising: a set of front wheels and a set
rear wheels provided on a machine body frame; a transmission case
arranged below the machine body frame; and a power transmission
device housed in the transmission case and configured to transmit a
driving power from an engine to driving wheels, the power
transmission device comprising: a front wheel driving shaft
arranged below the transmission case and configured to transmit the
driving power to the front wheels; and a four-wheel drive clutch
arranged offset from the front wheel driving shaft, wherein the
four-wheel drive clutch is configured to switch between a first
drive state in which the driving power is transmitted to the rear
wheels so that the rear wheels act as the driving wheels, and a
second drive state in which the driving power is transmitted to the
front wheels and the rear wheels via the front wheel driving shaft
so that both the front wheels and the rear wheels act as the
driving wheels, wherein the four-wheel drive clutch is arranged
adjacent to an inner wall of the transmission case, and wherein the
work vehicle further comprises: a sensor configured to detect
rotation of a gear for driving the four-wheel drive clutch, wherein
the sensor is provided in the inner wall of the transmission case.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
This application claims priority to Japanese Patent Application No.
2018-222695, filed Nov. 28, 2018, the disclosure of which is
incorporated herein by reference in its entirety.
BACKGROUND
The present disclosure relates to a work vehicle.
Conventionally, work vehicles have been known in which a power
transmission device is housed in a transmission case arranged below
a vehicle body and the power transmission device includes a front
wheel driving shaft for transmitting a driving power from an engine
to front wheels. Such work vehicles may also have a four-wheel
drive clutch for switching between a two-wheel drive (2WD) state in
which only rear wheels act as driving wheels, and a four-wheel
drive (4WD) state in which both the front wheels and the rear
wheels act as the driving wheels.
Also, among such work vehicles, there are work vehicles in which
the front wheel driving shaft is arranged in a lower inside portion
of the transmission case and the four-wheel drive clutch, which is
larger in diameter than the front wheel driving shaft, is provided
coaxially on the front wheel driving shaft (see e.g., Japanese
Patent Application Pub. No. JP-A-11-192849).
SUMMARY
However, in conventional work vehicles such as those described
above, the four-wheel drive clutch is provided coaxially on the
front wheel driving shaft arranged in the lower inside portion of
the transmission case. Therefore, a size of the transmission case
has to be increased in accordance with a size of the four-wheel
drive clutch, so that the four-wheel drive clutch can be housed
therein. Thus, the conventional work vehicles have room for
improvement in terms of downsizing the transmission case.
The present invention has been made keeping in mind the above
problems, and an object thereof is to provide a work vehicle, in
which downsizing of a transmission case may be achieved.
In order to address such technical concerns as those described
above and also to achieve the object, a work vehicle may be
provided. A work vehicle (1) according to a first aspect of the
present disclosure includes a pair of left and right front wheels
(4) and a pair of left and right rear wheels (5) each provided on a
machine body frame (2); a transmission case (6) arranged below the
machine body frame (2); and a power transmission device (7) housed
in the transmission case (6) and configured to transmit a driving
power from an engine (E) to driving wheels,
wherein the power transmission device (7) includes a front wheel
driving shaft (76) arranged in a lower inside portion of the
transmission case (6) and configured to transmit the driving power
to the front wheels (4); and a four-wheel drive clutch (78)
arranged at a location in the transmission case (6), which is
located above the front wheel driving shaft (76), wherein the
four-wheel drive clutch (78) is configured to switch between a
two-wheel drive state, in which the driving power is transmitted to
the rear wheels (5) and thus only the rear wheels (5) act as the
driving wheels, and a four-wheel drive state, in which the driving
power is transmitted to the front wheels (4) and the rear wheels
(5) via the front wheel driving shaft (76) and thus both the front
wheels (4) and the rear wheels (5) act as the driving wheels.
A work vehicle (1) according to a second aspect of the present
disclosure is the work vehicle (1) according to the first aspect
and further characterized in that the power transmission device (7)
further includes a rear wheel driving shaft (752) for driving the
rear wheels (5); and a four-wheel drive input shaft (79) configured
to receive the driving power from the rear wheel driving shaft
(752) and then to transmit the driving power to the four-wheel
drive clutch (78), wherein the four-wheel drive input shaft (79) is
provided coaxially with the front wheel driving shaft (76), and an
end portion (792) of the four-wheel drive input shaft (79) on a
downstream side in terms of power transmission is loosely fitted
with an end portion (762) of the front wheel driving shaft (76) on
an upstream side in terms of power transmission.
According to the first aspect of the present disclosure, the
four-wheel drive clutch, which may be larger in diameter than the
front wheel driving shaft, is not provided coaxially on the front
wheel driving shaft, but is arranged at a location in the
transmission case that is located above the front wheel driving
shaft. Therefore, it is possible to increase a ground clearance of
the transmission case and also to downsize and compactify the
transmission case.
According to the second aspect of the present invention, the
four-wheel drive input shaft is loosely fitted with the front wheel
driving shaft. Therefore, in addition to the effect of the first
aspect of the present invention, the effect is achieved that
positioning of the front wheel driving shaft, the four-wheel drive
input shaft and the four-wheel drive clutch can be easily performed
upon assembly of the power transmission device.
Objects and advantages of the disclosed embodiments may be realized
and attained by the elements and combinations that may be set forth
in the claims. However, embodiments of the present disclosure are
not necessarily required to achieve such exemplary objects and
advantages, and some embodiments may not achieve any of the objects
and advantages discussed above.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a schematic left side view showing a work vehicle
according to an embodiment.
FIG. 2 is a schematic plan view showing the work vehicle according
to the embodiment.
FIG. 3A is a schematic left side sectional view showing a power
transmission device.
FIG. 3B is an enlarged view of a section "a" shown in FIG. 3A.
DESCRIPTION OF EXEMPLARY EMBODIMENTS
Now, embodiments of a work vehicle disclosed herein will be
described in detail with reference to the accompanying drawings.
Meanwhile, the present invention is not limited to the embodiments
as described below.
Summary of Work Vehicle (Tractor) 1.
First, a summary of a work vehicle 1 will be described with
reference to FIGS. 1 and 2. FIG. 1 is a schematic left side view
showing a work vehicle 1 according to an embodiment. FIG. 2 is a
schematic plan view showing the work vehicle 1 according to the
embodiment. Meanwhile, in the following description, a tractor will
be described as an example of the work vehicle 1. The tractor 1,
which may be the work vehicle, is an agricultural tractor which is
intended to perform work on a farm field or the like while being
self-propelled.
Further, in the following description, a front and rear direction
is a travelling direction of the tractor 1 during straight travel,
and a front side of the travelling direction is defined as "front"
and a rear side thereof is defined as "rear". The travelling
direction of the tractor 1 is a direction from an operator seat 8
(as described below) toward a steering wheel 9 during straight
travel (see FIG. 2).
A left and right direction is a direction horizontally
perpendicular to the front and rear direction, and thus left and
right sides are defined toward the "front" side. That is, in a
state where an operator (also referred to as a worker) of the
tractor 1 sits on the operator seat 8 toward the front side, the
left hand side is defined as "left" and the right hand side is
defined as "right".
An upward and downward direction is a vertical direction. The front
and rear direction, the left and right direction and the upward and
downward direction are perpendicular to each other. Meanwhile, the
directions are defined for the sake of convenience of explanation,
and accordingly, the present invention is not limited to these
directions. Further, in the following description, the tractor 1
may also referred to as a "machine body".
As shown in FIGS. 1 and 2, the tractor 1 includes a machine body
frame 2, an engine E, a bonnet 3, front wheels 4, rear wheels 5 and
a transmission case 6. The machine body frame 2 is a main frame for
supporting the machine body. The engine E, which is a driving
source for the machine body, is a heat engine, such as a diesel
engine or a gasoline engine. The bonnet 3 is provided on a front
portion of the machine body to be opened and closed and thus to
cover the engine E in a closed state.
The front wheels 4 include a pair of right and left wheels and are
provided on a front portion of the machine body frame 2. The front
wheels 4 may be wheels for steering, i.e., steered wheels. The rear
wheels 5 include a pair of right and left wheels and are provided
on a rear portion of the machine body frame 2. The rear wheels 5
may be wheels for driving, i.e., driving wheels. Meanwhile, the
tractor 1 may be configured to be convertible between a two-wheel
drive (2WD), in which only the rear wheels 5 are driving wheels,
and a four-wheel drive (4WD), in which both the front wheels 4 and
the rear wheels 5 are driving wheels.
The transmission case 6 houses a power transmission device 7, which
is a speed-changing mechanism (see FIG. 3A). In the transmission
case 6, a driving power (rotational power) from the engine E is
transmitted to the driving wheels, as described below, or a PTO
(Power Take-off) shaft 50 (see FIG. 3A) after a speed thereof is
properly reduced by the power transmission device 7.
Also, the tractor 1 has an operator seat 8 and a steering wheel 9
on an upper portion of the machine body frame 2 and at the rear of
the bonnet 3, which constitute a cockpit of the tractor 1. The
operator seat 8 is provided on the rear portion of the machine body
frame 2. The operator seat 8 is a seat for an operator. The
steering wheel 9 is provided in front of the operator seat 8. The
steering wheel 9 is operated by the operator when steering the
front wheels 4, which are also the steered wheels.
Further, in addition to the operator seat 8 and the steering wheel
9, the cockpit of the tractor 1 includes a meter panel for
displaying various information; various operation pedals, such as
an accelerator pedal, a clutch pedal and a brake pedal; and various
operation levers, such as a forward/reverse lever, a main shift
lever and a sub-shift lever.
Also, the tractor 1 has a work machine, such as a rotary tiller,
mounted, for example, on the rear of the machine body. The work
machine is driven by the PTO shaft 50 protruding rearward from the
rear portion of the transmission case 6. The PTO shaft 50 is
configured to transmit the rotational power, which is outputted
from the engine E, to the work machine, which is performing work on
a farm field. In addition to the PTO shaft 50, the tractor 1 has a
lift arm for connecting the work machine thereto and the like at
the rear of the machine body.
Further, the tractor 1 may have a mid-mower M, such a lawn mower
(see FIG. 3A), provided below the machine body, e.g., between the
transmission case 6 and a ground surface G.
Power Transmission Device 7
Next, the power transmission device 7 will be described with
reference to FIGS. 3A and 3B. FIG. 3A is a schematic left side
sectional view showing the power transmission device 7. FIG. 3B is
an enlarged view of a section "a" shown in FIG. 3A and corresponds
to a schematic left side sectional view showing a four-wheel drive
clutch 78. Meanwhile, in the example shown in FIG. 3A, the
mid-mower M, such as a lawn mower, is provided between the
transmission case 6 and the ground surface G.
As shown in FIG. 3A and also described above, the power
transmission device 7 is housed in the transmission case 6 arranged
below the machine body frame 2 (see FIG. 1). The transmission case
6 is a hollow case and is formed by connecting three members, for
example, a front case, a mid-case and a rear case, with each other
in the front and rear direction.
As shown in FIG. 3A, an input shaft 70 is connected to the power
transmission device 7 via a main clutch 71. The power transmission
device 7 has a speed-changing mechanism configured to speed-change
a rotational power from the engine E (see FIG. 1) and then to
output the rotational power to various parts. Meanwhile, the input
shaft 70 is also an input shaft of the speed-changing
mechanism.
The speed-changing mechanism includes a hydrostatic continuously
variable transmission 72, which is configured to switch
forward/reverse stages and main shift stages, and a
sub-transmission mechanism 75. Meanwhile, the hydrostatic
continuously variable transmission 72 can continuously change
forward and reverse gear ratios and other gear shift ratios, and
the sub-transmission mechanism 75 has a plurality of shift
stages.
The hydrostatic continuously variable transmission 72 can transmits
the rotational power, which is inputted to the input shaft 70
thereof, to a main shift output shaft 731. Also, when transmitting
the rotational power to the main shift output shaft 731, the
hydrostatic continuously variable transmission 72 can transmit the
rotational power after switching a rotation direction thereof
depending on operation of the forward/reverse lever.
Further, the hydrostatic continuously variable transmission 72 can
continuously change a ratio of a rotational speed of the main shift
output shaft 731 to a rotational speed of the input shaft 70 by
changing a capacity of a piston acting on a hydraulic pump and a
hydraulic motor, both which are provided inside the hydrostatic
continuously variable transmission 72.
The sub-transmission mechanism (sub-transmission synchromesh) 75
can receive the rotational power from the hydrostatic continuously
variable transmission 72 via a sub-transmission mechanism input
portion 751 provided on a PTO drive shaft 742. The sub-transmission
mechanism 75 can output the rotational power, which is received
from the hydrostatic continuously variable transmission 72, via a
rear wheel driving shaft 752, which is an output shaft of the
sub-transmission mechanism 75, after changing a gear shift ratio
thereof depending on operation of the sub-shift lever.
Also, the power transmission device 7 includes a PTO output
mechanism, a PTO clutch 74 and a PTO speed-changing device. The PTO
output mechanism is configured to transmit the rotational power
from the engine E to the PTO shaft 50. The PTO output mechanism can
receive the rotational power from the input shaft 70.
The PTO clutch is configured to switch between "ON (connection)"
and "OFF (disconnection)" of the rotational power toward the PTO
shaft 50. The PTO clutch 74 is a multiplate friction clutch
operated by a hydraulic pressure, e.g., a hydraulic clutch. The PTO
speed-changing device is configured to speed-change the power to be
transmitted to the PTO shaft 50.
In addition, the tractor 1 may have a sensitivity adjusting dial
for changing (e.g., adjusting) a degree of pressure increase of the
hydraulic pressure (e.g., pressure of hydraulic oil) upon
connection of the PTO clutch 74, so that the operator can manually
switch the sensitivity adjusting dial depending on the type of
work. Thus, connection of the PTO clutch can be properly performed
such that a clutch connection sensitivity becomes good, and the
like.
Further, as shown in FIGS. 3A and 3B, the power transmission device
7 has a front wheel driving shaft 76, a rear-wheel-power-diverter
shaft 77, a four-wheel drive clutch 78 and a four-wheel drive input
shaft 79.
The front wheel driving shaft 76 is arranged in a lower inside
portion of the transmission case 6 so as to extend in the front and
rear direction inside the transmission case 6. The front wheel
driving shaft 76 is configured to transmit the rotational power
from the engine E to the front wheels 4 (see FIGS. 1 and 2),
thereby driving the front wheels 4.
The rear-wheel-power-diverter shaft 77 is configured to receive a
rotational power diverted from the rear wheel driving shaft 752 for
driving the rear wheels 5 (see FIGS. 1 and 2). The four-wheel drive
clutch 78 is configured to cause the rotation power, which is
transmitted from the rear-wheel-power-diverter shaft 77 to the
four-wheel drive input shaft 79, to be switched between "ON
(connection)" and "OFF (disconnection)" with respect to the front
wheel driving shaft 76. The four-wheel drive clutch 78 is a
multiplate friction clutch operated by a hydraulic pressure, e.g.,
a hydraulic clutch.
Also, the four-wheel drive clutch 78 is configured to switch
between a state in which the rotational power is transmitted from
the rear wheel driving shaft 752 to the front wheels 4, and a state
in which the rotational power is not transmitted to the front
wheels 4, thereby switching between the four-wheel drive (4WD) and
the two-wheel drive (2WD).
Specifically, if the four-wheel drive clutch 78 is connected, the
rotational power inputted thereto through an input gear 782 is
transmitted to an output gear 781 via the four-wheel drive clutch
78, and then the rotational power is transmitted to the front wheel
driving shaft 76 through a gear 761. Therefore, the tractor 1
enters a four-wheel drive (4WD) state, in which both the front
wheels 4 and the rear wheels 5 act as driving wheels.
In addition, the power transmission device 7 may further include a
front wheel multiplying gear. In this case, for example, if the
four-wheel drive clutch 78 is connected to the front wheel
multiplying gear, the rotational power outputted from the output
gear 781 via the four-wheel drive clutch 78 is speed-increased, for
example, through a first multiplying gear, a second multiplying
gear and the like, and then transmitted to the front wheel driving
shaft 76. In this way, a four-wheel drive (4WD) configuration
having a multiplied front wheel speed can be obtained.
If the four-wheel drive clutch 78 becomes a neutral state, no
rotational power is transmitted to the front wheels 4. As a result,
the tractor 1 enters a two-wheel drive (2WD) state, in which only
the rear wheels 5 act as driving wheels.
Herein, the four-wheel drive clutch 78 has a diameter larger than
the front wheel driving shaft 76. For example, if the four-wheel
drive clutch 78 is provided coaxially on the front wheel driving
shaft 76, a space for receiving therein the four-wheel drive clutch
78, which is larger in diameter than the front wheel driving shaft
76, has to be secured in the lower inside portion of the
transmission case 6, thereby hindering downsizing of the
transmission case 6. Therefore, in order to achieve downsizing of
the transmission case 6, the present embodiment has a configuration
in which the four-wheel drive clutch 78 is not provided on the
front wheel driving shaft 76. Rather, the four-wheel drive clutch
78 may be arranged offset from the front wheel driving shaft
76.
Specifically, the four-wheel drive clutch 78 is provided on a
separate shaft from the front wheel driving shaft 76. The
four-wheel drive clutch 78 is arranged at a location in the
transmission case 6 that is located above the front wheel driving
shaft 76. The four-wheel drive input shaft 79 is configured to
transmit the rotational power from the rear-wheel-power-diverter
shaft 77 to the four-wheel drive clutch 78 through the gear 791. In
addition, the four-wheel drive clutch 78 is preferably arranged to
be offset from the front wheel driving shaft 76 in the left and
right direction as well as the upward and downward direction. That
is, the four-wheel drive clutch 78 is arranged obliquely above the
front wheel driving shaft 76.
Further, the four-wheel drive input shaft 79 is provided coaxially
with the front wheel driving shaft 76 in such a manner that an end
portion 792 thereof, which corresponds to a downstream side in
terms of power transmission, faces an end portion 762 of the front
wheel driving shaft 76, which corresponds to an upstream side in
terms of power transmission. A circular-cylindrical convex portion
792a provided on an end surface of the end portion 792 of the
four-wheel drive input shaft 79 is fitted into a circular concave
portion 762a formed on an end surface of the end portion 762 of the
front wheel driving shaft 76. In this case, the convex portion 792a
of the end portion 792 of the four-wheel drive input shaft 79 is
loosely fitted into the concave portion 762a of the end portion 762
of the front wheel driving shaft 76, so that a gap is defined
between the convex portion 792a and an inner wall of the concave
portion 762a.
Meanwhile, the transmission case 6 is configured such that an inner
wall thereof is arranged close to the four-wheel drive clutch 78.
The inner wall may be adjacent to the four-wheel drive clutch 78.
Also, a boss is provided on the inner wall of the transmission case
6. The boss has a rotational sensor attached thereto. The
rotational sensor is configured to detect rotation of a gear for
driving the four-wheel drive clutch 78, for example, unevenness of
the gear in a non-contact manner. For example, the rotational
sensor may be configured to sense a tooth of a gear passing by the
sensor. By configuring in this way, a rotational speed can be
detected using a rotational shaft at the rear stage of the
sub-transmission mechanism 75, e.g., on a downstream side of the
sub-transmission mechanism 75 in terms of power transmission,
thereby allowing detection of a vehicle speed regardless of a
position of the sub-transmission mechanism 75.
In this case, the rotational sensor is preferably provided in a
groove formed in an outer circumferential surface of the four-wheel
drive clutch 78. In this way, the rotational sensor is provided at
a location close to the inner wall of the transmission case 6,
thereby facilitating attachment of the rotational sensor.
According to the work vehicle 1 of the foregoing embodiment, the
four-wheel drive clutch 78, which is larger in diameter than the
front wheel driving shaft 76, is not provided coaxially on the
front wheel driving shaft 76, but arranged at a location in the
transmission case 6, which is located above the front wheel driving
shaft 76. Therefore, it is possible to increase a ground clearance
h of the transmission case 6 and also to downsize and compactify
the transmission case 6.
Also, in the case where a mid-mower M, such as a lawn mower, is
provided below the transmission case 6, a space required to lift
the mid-mower M can be secured due to the increased ground
clearance h of the transmission case 6. The mid-mower M may be one
example of an implement powered by the engine E that is provided
below the transmission case 6.
Further, the input gear 782 and the output gear 781 for the
four-wheel drive clutch 78 are provided to sandwich the four-wheel
drive clutch 78 at front and rear sides thereof. The gear 791 of
the four-wheel drive input shaft 79 is provided at the same
position as that of the input gear 782 in terms of a front and rear
direction positional relationship, and the gear 761 of the front
wheel driving shaft 76 is provided at the same position as that of
the output gear 781 in terms of the front and rear direction
positional relationship.
In addition, between the gear 791 of the four-wheel drive input
shaft 79 and the gear 761 of the front wheel driving shaft 76, the
four-wheel drive input shaft 79 is loosely fitted with the front
wheel driving shaft 76. Therefore, upon assembly of the power
transmission device 7, positioning of the front wheel driving shaft
76, the four-wheel drive input shaft 79 and the four-wheel drive
clutch 78 can be performed in a compact and easy manner without
using new bearings.
As a result, the four-wheel drive clutch 78, which is larger in
diameter than that of the front wheel driving shaft 76, can be
arranged close to the front wheel driving shaft 76 and the
four-wheel drive input shaft 79 in such a manner to enter between
the gear 791 and the gear 761. Meanwhile, even if the four-wheel
drive input shaft 79 is loosely fitted into the front wheel driving
shaft 76, there is no significant difference in rotational speed
between the front wheel driving shaft 76 and the four-wheel drive
input shaft 79 during travelling regardless of "ON (connection)"
and "OFF (disconnection)" of the four-wheel drive clutch 78.
Therefore, there is little influence by friction.
Herein, the four-wheel drive clutch 78 has a relatively high
rotational speed. The four-wheel drive clutch 78 may be a wet
clutch. Therefore, as the four-wheel drive clutch 78 rotates at a
high speed while being bathed in oil inside the transmission case
6, a large loss in horsepower may occur. For this reason, according
to the work vehicle 1 of the present embodiment, the four-wheel
drive input shaft 79 has a gear ratio set to be lower than that of
the front wheel driving shaft 76. As a result, it is possible to
limit the rotational speed of the four-wheel drive clutch 78,
thereby reducing a horsepower loss.
In this case, rotation of a gear connected to the four-wheel drive
clutch 78 to drive the four-wheel drive clutch 78, for example,
unevenness of the gear is detected with the rotational sensor in a
non-contact manner. Also, the rotational sensor is provided at a
location close to the inner wall of the transmission case 6,
thereby facilitating attachment of the rotational sensor.
Alternatively, the four-wheel drive input shaft 79 may have a gear
ratio set to be higher than that of the front wheel driving shaft
76. By increasing a speed of the four-wheel drive input shaft 79, a
torque of the four-wheel drive input shaft 79 is decreased.
Accordingly, a compact clutch having a small capacity can be used
as the four-wheel drive clutch 78.
Further effects and variants can be easily derived by those skilled
in the art. Therefore, broader aspects of the present invention are
not limited to the specific details and representative embodiments
as shown and described above. Accordingly, various modifications
can be made without departing from the spirit or scope of the
general inventive concept as may be defined by the claims and
equivalents thereof.
REFERENCE SIGNS LIST
1: Work vehicle (tractor) 2: Machine body frame 3: Bonnet 4: Front
wheel 5: Rear wheel 6: Transmission case 7: Power transmission
device 70: Input shaft 71: Main clutch 72: Hydrostatic continuously
variable transmission 731: Main shift output shaft 74: PTO clutch
742: PTO drive shaft 75: Sub-transmission mechanism 751:
Sub-transmission mechanism input portion 752: Rear wheel driving
shaft 76: Front wheel driving shaft 761: Gear 762: End portion
762a: Concave portion 77: Rear-wheel-power-diverter shaft 78:
Four-wheel drive clutch 781: Output gear 782: Input gear 79:
Four-wheel drive input shaft 791: Gear 792: End portion 792a:
Convex portion 8: Operator seat 9: Steering wheel E: Engine G:
Ground surface h: Ground clearance M: Mid-mower
* * * * *